Exercise regimens for developing cardiorespiratory conditioning are known. The goal of such conditioning is to increase and sustain cardiac output, as well as develop the ability of the lungs to extract sufficient oxygen from the environment and to eliminate carbon dioxide which builds up as a result of increased muscle metabolism, to thus enable the individual to participate and/or compete in endurance sports, events, or activities such as distance running, cycling, rowing, soccer, etc.
To help achieve that end, the fitness industry, through the development of new exercise devices, has now made available to the general public a variety of means to exercise and become more physically fit. Among the more recent innovations include the development of programmable exercise devices, such as treadmills, stationary cycles, and stair climbers, which enable the user to "customize" a particular workout regimen based upon certain data provided by the user via a digital interface. Typically, the user must supply information regarding his or her weight, age, etc. which consequently causes the exercise device to implement an exercise regimen that strives to attain optimal cardiorespiratory conditioning, typically by maintaining the exercise regimen within the specified training intensity for a fixed duration.
Recent research tends to indicate that optimal cardiorespiratory conditioning occurs when an individual exercises at a training intensity at or above the Anaerobic Threshold (AT) (i.e., the point at which the subject can no longer provide all of the energy necessary to perform that workload with only aerobic metabolism). Because the terminology in the ever-evolving field of fitness is varied, it is understood in the art that the term Anaerobic Threshold may additionally be referred to as the Lactic Acid Threshold, Onset of Blood Lactate Accumulation (OBLA), Gas Exchange Threshold, Ventilatory Threshold, and/or Metabolic Acidosis Threshold. At exercise intensities above the AT, carbohydrates are anaerobically metabolized into lactic acid, as opposed to pyruvate under aerobic metabolism. While the body is able to clear (i.e., metabolize) some lactic acid, a point is eventually reached whereby the lactic acid begins to accumulate in the muscles and bloodstream, eventually causing muscle soreness and fatigue.
Novel research now tends to indicate that for the trained, highly-conditioned athlete cardiorespiratory conditioning can be achieved by exercising for short durations near the individual's Respiratory Compensation Point (RCP) (the point at which the individual is most physically active and is characterized by a marked increase in ventilation and CO.sub.2 production) and, for the most well-conditioned athletes, near the individual's maximum oxygen consumption (VO.sub.2 max). When the individual exercises at or near his or her RCP, the excess of lactic acid produced by the muscles acidifies the blood and causes the individual to hyperventilate and expire as much CO.sub.2 as possible. Eventually, the individual must default the exercise, typically within 60 to 120 seconds after having reached the RCP, particularly if the work rate continues to increase. To the extent the individual is capable of sustaining a greater work load during the individual's RCP, albeit for a very brief period, the individual eventually reaches his or her VO.sub.2 max, which coincides with the individual's inability to engage in any further physical activity insofar as the symptoms of exhaustion overwhelm the individual's system.
While methods are available for determining the point at which an individual reaches his or her Anaerobic Threshold and Respiratory Compensation Point, typically via gas exchange tests that detect an increase in expired minute ventilation (VE), oxygen uptake (VO.sub.2) or carbon dioxide output (VCO.sub.2), such tests have not heretofore been applied for purposes of constructing an exercise regimen centered around training intensities that specifically target the individual's Anaerobic Threshold and Respiratory Compensation Point, let alone identify specific durations at which a given exercise is to be performed at a given training intensity. In this respect, the relative inaccessibility of the sophisticated equipment and trained staff needed to conduct aerobic fitness tests, interpret the results, and use these results to develop rational training programs has prevented the widespread use of scientific knowledge among those wishing to optimize their aerobic fitness.
In an attempt to provide some objective standard, guidelines from the American College of Sports Medicine (ACSM) have suggested training intensities based on percentages of maximal oxygen uptake (VO.sub.2 max), percentages of the heart rate (HR) reserve (HRres, which is HRmax-HRrest), or percentages of HRmax, which typically fall within the range from 40-90% of these variables. To date, however, no explicit guidelines have been determined regarding which percentage or individual state of training is best for whom, and under what training conditions. For example, two people could both be given a training intensity of 70% of the HRres. One individual might carry out this recommendation within the aerobic domain (below the lactic acidosis threshold) while the other person might be above it. While both people train at the same percentage of the HRres, each experiences a different metabolic requirement for adenosine triphosphate (energy) production. One may be able to sustain the activity quite a bit longer (below the Anaerobic Threshold) while the other will be limited in his/her ability to continue work by lactic acid accumulation. As such, issues arise as to whether both people are training at the same intensity.
Further compounding the difficulties in prescribing exercise intensities is the common practice of estimating the maximum heart rate for use in generating a training heart rate (THR). One approach to this calculation is the 220-minus-age method. However, the error associated with this estimate has been reported as 10-15 beats per minute.
Some practitioners prescribe exercise intensities on the basis of a percentage of VO.sub.2 max. Often (if not usually) VO.sub.2 max is not actually measured in the fitness center or health club setting. Rather, VO.sub.2 max is estimated from the heart rate-work rate (WR) relationship obtained from a sub-maximal test. Maximal work rate is then predicted by extrapolating the HR-WR curve to an estimated (i.e., 220 minus age) HRmax. Errors in estimating VO.sub.2 max by this approach average about 15% and have been reported to be as high as 25%.
In this regard, if maximal HRs are distributed normally in the population, the mean (average) HR will occur at 220 minus age. One standard deviation (SD) from this mean would be .+-.10 beats per minute. For example, a 30-year-old would have a predicted HRmax of 220 minus 30 or 190 beats per minute. Statistically, 68% of these people aged 30 would have a maximal HR between 180 and 200 beats per minute. However, this range does not include the remaining 32% of people 30 years of age. Moving out two standard deviations will capture more 30-year-olds (95% of the population), but the range of HRmax will now increase and by 10 more beats per minute on each side of the mean, yielding 170-210 beats per minute. At this point, approximately 5% of the 30-year-old population would still not be accounted for. Moving out one more standard deviation will include 99% of the population, but the range of HRmax would fall between 160-220 beats per minute. As a consequence, for every 100 people of age 30 encountered, roughly 68 of them will have a HRmax between 180 and 200 beats per minute.
To illustrate this concept, if a resting HR (HRrest) of 70 beats per minute is assumed, the familiar Karvonen formula (220 minus age) and an arbitrary intensity value of 70% of the HRrest would yield a training heart rate of 154 beats per minute for the average 30-year-old. An error up to 1 SD from the mean would over- or under-estimate the THR by .+-.7 beats per minute. However, the farther the movement away from the mean, the greater the error. Even at .+-.2 SD from the mean, the THR error is .+-.14 beats per minute and .+-.21 beats per minute for the rare individual who is .+-.3 SD from the mean.
As opposed to the aforementioned methodology using assumptions or estimates for implementing exercise regimens at specified training intensities, attempts have been made to personally assess cardiorespiratory fitness and construct individual training programs based upon such evaluation.
The most typical cardiorespiratory fitness test used in health clubs and fitness centers is the sub-maximal cycle ergometer test. Such standardized test, however, is problematic for several reasons. First, use of the cycle ergometer may violate the law of specificity in that not all individuals who undergo a cycle ergometer test will train on the cycle ergometer. Thus, the extent to which a person improves aerobic capacity may not be truly identified if the individual uses a different mode of exercise for training, such as jogging. Second, sub-maximal tests have potentially large errors in predicting VO.sub.2 max, namely, the maximal amount of oxygen that can be used for energy production during exhaustive exercise. The VO.sub.2 max occurs beyond RCP and is a measure of the individual's endurance exercise capacity and cardiorespiratory functional capacity. Third, identification and use of the Anaerobic Threshold is impossible without either blood samples analyzed for lactic acid or measurements of gas exchange. As such, due to the unique physiological responses of every individual, coupled with the different types of physical conditioning provided by different types of exercise equipment, an exercise regimen that truly optimizes cardiorespiratory fitness is rarely, if ever, implemented.
Separate and apart from the foregoing, the ideal approach would be to customize or specifically tailor an exercise regimen using identifiable training intensities based upon an individual's specific cardiorespiratory function, as identified by the specific physiological markers unique to that individual. As discussed above, studies investigating intensities of training typically report that the greatest improvements in aerobic function occur at the highest training intensities. Nevertheless, unanswered questions still persist as to what training intensity brings optimal results, how training intensity should be determined and manipulated, and whether one training intensity is appropriate for optimal benefit. Accordingly, there is a need in the art for systems and methods for assessing an individual's cardiorespiratory fitness and determining the specific training intensities that the individual can strive for that optimize his or her cardiorespiratory conditioning. There is further a need in the art for systems and methods for not only identifying such training intensities, but for exercise regimens that are centered around such training intensities that can be utilized to more rapidly increase endurance and cardiorespiratory conditioning than prior art methods. There is still further a need in the art for systems and methods for exercise regimens utilizing training intensities that are custom tailored to suit the needs of a particular individual that can be applied to any of a variety of cardiorespiratory exercise devices, including, but not limited to treadmills, stationary bicycles and/or stair climbers.